Zig smart pointers

Zig smart pointers. Zig implements dynamic dispatch via a pattern where a struct of function pointers is nested in an outer struct containing closed-over data. Qt had smart pointers much before the modern c++. This is particularly useful in the context of OOP, to store a pointer as a member variable and return it to access the referenced value outside the scope of the class. C++11 has introduced three types of smart pointers, all of them defined in the <memory> header from the Standard Library: std::unique_ptr — a smart pointer that owns a dynamically allocated resource; std::shared_ptr — a smart pointer that owns a shared dynamically allocated resource. The smart pointer will delete the pointed-to object at the right time including invoking the object’s destructor. com/contextfreecode/safety0:00 Intro0:33 C++ (cpp)3:18 Zig3:41 Rust5:13 C#7:16 C# with struct Single-item pointers are values that store the pointer to another value. In that case, you won't need to create an additional smart pointer over it, and you will be Oct 10, 2022 · I think smart pointers have to be introduced as it's hard to manually free all dynamic allocated memory in a growing project. Smart pointers, in plain terms, are classes that wrap a pointer, or scoped pointers. ptr = f(std::move(ptr)); Dec 29, 2023 · Zig allows us to write Zig code (no special macro syntax like in Rust), which is evaluated during compile time using the comptime keyword. {s. Current blog posts and consolidated historical articles from various other blog platforms used previously - blog/2022/20220831-zig-pointer-cheatsheet. Notice how this function is PascalCase, as it returns a type. zig Slices. smart_pointer_type is the type of smart pointer that you wish to use such as unique_ptr, shared_ptr, or weak_ptr. Zig is an open-source programming language designed for robustness , optimality, and clarity . framebufferResized = true; } observable: : Unique-ownership smart pointers with observable lifetime. Reference counted (e. Slices are a special kind of pointer that reference a contiguous subset of elements in a sequence. Smart pointers also provide additional functionality for references. Feb 22, 2019 · This is what I see on my machine if I build and run the above code: 1 ~ $ clang++ -std=c++17 -Wall -pedantic -O2 SLList_02. TL;DR: Use null terminated arryas (pointers, slices) only when you absolutely have to (interface to C). Apr 8, 2022 · Smart pointers are helpful, but a complete understanding is a must. Pointers. print; The easiest way to understand slices is to think of them as a single-item pointer plus a length. You can turn an array or pointer into a slice using slice syntax. zig has special [*c]T for c pointer. The six rules violate the import dry ( don’t repeat yourself) principle for software development. “C++ is safe if you use smart pointers and collections” is just a dangerous fantasy. fn framebufferResizeCallback(window: ?*cInclude. Aug 31, 2022 · Do not share my personal information. be/qeiRGbYCD-0Source code: https://github. Jul 6, 2020 · The shared_pointer is a reference counting smart pointer that can be used to store and pass a reference beyond the scope of a function. However, dynamic memory allocations are not allowed during compile time. Smart pointers should be preferred over raw pointers. 2 Likes. Just found issue #782 while researching async stuff. Copy. With Aurora, it's trivial to implement deep-copy through smart pointers. You don't see in that examples because QObject handles all the child / parents related issues and there life cycle. andrewrk 1 year ago | link. They follow the syntax *T, where T is the child type. The second happens much more often: smart manager means ownership. To convince the compiler that this is fine std::move can be used. 10, there are 2 ways to pass a function as an argument: As a function body. Which apparently are pointers to an unknown number of items. Pointers are smart dogs. Jan 11, 2024 · Smart Pointer. This makes it often unnecessary to implement The Big Three/Five if your classes have pointer members. This tutorial covers C data types, FFI, building with C, translate-c Feb 5, 2024 · Zig 2024 roadmap. Again, check language spec here. Their syntax is []T, with T being the child type. Each year we have *some* memory bugs (and none in production) but hundreds of logic errors. [3] It is intended as a successor to the language C, with the intent of being even smaller and simpler to program in, while offering more function. Aug 30, 2021 · Zig knows the memory layout and can calculate how much it needs to subtract from a member pointer to get to the beginning of a struct. It returns a pointer to the enclosing struct (pick_random). By including <memory>, we gain access to the std::make_unique function. These pointers, as the name implies are able to automatically delete themselves when they go out of scope, removing the need for you to do it yourself. 3 min read. A smart pointer looks and behaves like a regular C++ pointer. glfwGetWindowUserPointer(window)); app. In Zig, we prefer slices over pointers to null-terminated arrays. The type of a pointer is an asterisk (*) before the type of the value to which it points. 009s This is thanks to Build Artifact Caching. test. Sep 25, 2022 · If your local variable foo is mutable and the function call receives a non-const pointer to it, you can use it without any decoration and Zig will do the rest. Smart pointers can also be used to manage other resources like network connections. This saves us from many issues that using the new and delete keywords can bring. Like in Rust, Zig types are zero-cost abstractions. Slices can be thought of as a pair of [*]T (the pointer to the data) and a usize (the element count). They handle their own memory management, which means fewer chances of memory leaks, null pointer dereferencing, and other pointer-related $ zig test pointer_casting. Let say anecdotal. When the owning std::unique_ptr is destroyed or reset, it automatically destructs the objects and releases its memory. pointer arithmetic with slicesOK All 2 tests passed. Given a pointer to a struct field, along with that field's name and the struct's type, it will return a pointer to the struct. It appears that Zig may be safer than Unsafe Rust. There are two situations where you should not use smart pointers. $ zig test test_pointer_arithmetic. x branch) - uses zig build-system; cppfront: Build Cppfront w/ zig build; hana: Your standard library for Aug 31, 2022 · Pointers and constness in Zig (and why it is confusing to a C programmer) # pointers # const # c # learn. A pointer is a variable that maintains a memory address as well as data type information about that memory location. 2 Likes jiacai2050 September 26, 2022, 3:18pm Apr 28, 2017 · std::shared_ptr<int> c = std::dynamic_pointer_cast<int>(b); void and int do not have an inheritance relationship so they can not be up- or down casted. Not only can Zig compile C code, but there is a very good reason to use Zig as a C compiler: Zig ships with libc. Feedback and PRs are welcome. The only other similar behavior that I can think of is [] syntax used on arrays. Jun 4, 2019 · The Intelligence of Pointers. $ time zig build-exe hello. Apr 12, 2023 · In modern C++ programming, memory management is a crucial aspect of writing efficient, maintainable, and bug-free code. The pointer tells you where the slice begins and the length tells Feb 20, 2009 · Basic properties of smart pointers. I’m trying to get a clear understanding of stack allocations, and their lifetime attached to their stack frame. Simple sole ownership of arrays. C) void { var app = @as(*HelloTriangleApplication, cInclude. pointer_name is the name of the pointer try expect(b == 5); try expect(@TypeOf(b) == f32); } Function parameters in Zig can be tagged as being comptime. This address refers to, or “points at,” some other data. They hold everything up but can also bring it all down if you’re not careful. const self = @fieldParentPtr(Self, "iterator", iterator); Oct 19, 2020 · 1 is a mistake I also regularly make in unsafe rust too - clearly I can't be trusted with pointers :S. Mar 10, 2014 · Still, smart pointers were old hat at that point, so the report considered also that. Aug 31, 2022 · Hello (Zig) World! since I'm still not automatically remembering all the various combinatorial possibilities of different types of pointers, slices, const ness and optionals, I've finally taken the plunge and created a little cheatsheet for quick reference. const std = @import("std"); const print = std. 8. The zig language reference is a bit muddled about this, as it does say to use anyopaque for type erased pointers. . The following code works for any copyable type T: aurora::CopiedPtr<T> first(new T); aurora::CopiedPtr<T> second = first; // deep copy. pointer arithmetic with many-item pointerOK 2/2 test_pointer_arithmetic. If m is a hash map, m [i] = m [j] is a memory safety bug. May 17, 2022 · var s: S = . This is how null pointers in Zig work - they must be unwrapped to a non-optional before dereferencing, which stops null pointer dereferences from happening accidentally. – sanjay. These operations are performed on each of the values in the vector. Sometimes, you may have a pointer to an unknown number of elements. Nov 5, 2023 · With smart pointers, you no longer need to manually release memory. Here, we've had to assign values to _, as Zig does not allow us to have unused values. It's easy when you have properties that you can assign each smart pointer. Is there a better way of doing this so that I don't have to write @intToPtr(?*T, 0)) every time I need a NULL pointer (of course a very common occurrence when interfacing with C libraries) I tried searching for a solution Aug 14, 2010 · Smart Pointer types are an abstraction layer to automate the process of allocation and deallocation of memory, their constructor function, gets an allocated memory (via pointer) and their destructor function, frees the allocated memory. ptr = aFunction }; print("{}\n", . tech/c-cpp-newsletterSmart pointers can Sep 8, 2023 · Pointers are like the scaffolding of C programming. push_back(new int(i)); Initializing a vector of pointers to newly allocated objects (needs C++11): std::vector<int*> widgets Jul 20, 2021 · For 1 and 2, you are correct. smart pointer is an object that stores a pointer to a heap-allocated object. Here's a little bit of sample Zig code, along with its associated memory. *T coerces to [*]T. This code will not compile, as there is no copying of the std::unique_ptr. It's not exhaustive, but should cover most real world cases nobody said it'd be easy! Apr 5, 2023 · The dot operator is used for pointer dereferencing and distinguishing between single and array value pointers. RAII is an excellent option to default to, but in Zig you aren't allowed to. Smart Pointers. So . This can help to optimize the code and allows for reflection on types. Quoting the relevant part: “if accessing a value through a trivial smart pointer is significantly slower than accessing it through an ordinary pointer, the compiler is inefficiently handling the abstraction. io/Smart_Pointers. After this, the list nodes will be recursively destroyed! 4 Segmentation fault: 11 5 ~ $. Also, I suggest you use *anyopaque for the argument type if you expect them to commonly be type erased pointers. References are indicated by the & symbol and borrow the value they point to. no ownership at all. $ zig test test. org/---Back to Basics: C++ Smart Pointers - David Olsen - CppCon 2022https://github. std::unique_ptr is a smart pointer that owns the object exclusively. The standard library's smart pointers can be customized in the way they handle the de-allocation of the memory they hold. ptr(5)}); Right now, functions are implicitly pointers, so all you need to do is use the name of a function in an assignment to a function pointer variable (or here a member of a struct). { str }); Apr 21, 2022 · C++ Smart Pointers. and data_type is the data type of the pointer variable. Operations between vectors with the same child type and length can take place. Nov 21, 2022 · Part 1: https://youtu. 1668553684. transfer of ownership. The natural Zig code equivalent would look like Jun 10, 2023 · Hopefully the Zig ecosystem will evolve an address sanitizer like Clang’s (and GCC has one too I think?) At this point I’d hate to develop in C++, let alone C, without it. Karsten Schmidt. Mar 15, 2024 · One of my bigger issues with Zig is that it doesn't support RAII. Optimal - write programs the best way they can behave and perform. This is because internally they use the 0 value of the pointer for null. Slices have the same attributes as pointers, meaning that there also exists const slices. Sep 20, 2008 · A smart pointer is a class that wraps a 'raw' (or 'bare') C++ pointer, to manage the lifetime of the object being pointed to. 16 reactions. There are three important properties. [*]T is the solution for this, which works like *T but also supports indexing syntax, pointer arithmetic, and slicing. Referencing is done with &variable, and dereferencing is done with variable. Sep 20, 2022 · new data_type () is how we will generally create a normal pointer and we immediately pass that to a smart pointer constructor where. However there is a bug: test. Nov 1, 2018 · Types of smart pointers in modern C++. One tricky thing worth talking more is pointers. int* ptr = new int(5); delete ptr; *ptr = 10; // ptr is dangling after delete Use Smart Pointers. I don't think smart pointer and optional types are the same. In Zig, you can get the address of any value by using the address-of operator &. Packed structs have 1-byte alignment. The type of a pointer is an asterisk ( *) before the type of the value to which it points. C++. Obviously, this is a serious bug in our code. Quickly glancing at zig official website , this looks like a mistake Dec 27, 2022 · I want to check if a pointer to any kind of object (in this case, a nullable [of course] pointer to a GLFWwindow) is NULL. Your object only tied to its parent lifespan. Memory management is part of data structures, so you might learn more, if you use raw pointers. Dec 1, 2023 · Hello there, I’m learning zig, coming from higher level languages (go, mostly). It’s a pointer-wrapping stack-allocated object. com/CppCon/CppCon2022Smart pointers were one of the many p Dec 23, 2015 · 10. std. test "for" {. show Oct 21, 2017 · Your object is a QWidget, of course, or GUI related. The first means that a smart pointer cannot delete the object, because it doesn't own it. As human beings, we thrive off of having the best. void SmartPointerDemo2() {. Dec 26, 2023 · Last but not least, memory savings from not storing length field is rarely realized, for allocator’s alignment will pad null byte all way up to 4 or 8 bytes, the same size as the lenght field. Feb 17, 2022 · Newb Question: the linked post "the-missing-zig-polymorphism-reference" says: You could also use anyopaque but it introduces alignment problems that only complicates the solution. Conversely, a smart pointer can be converted to true if it owns something. Of course the constructor and the destructor can be inlined (thus there is no overhead to call them). A smart pointer is an object that stores a pointer to a heap-allocated object. Have to say it doesn't really sit right with me. std. However, all pointers are implicitly convertible to a void pointer, so an implicit conversion is possible: std::shared_ptr<void> b = a; Mar 2, 2024 · Many-item Pointers. RAII, smart pointers, references, even templates can make a huge difference in Aug 17, 2023 · Dangling pointers refer to memory locations that have been deallocated. For loops are used to iterate over arrays (and other types, to be discussed later). There are a lot of things that go into their intelligence, and it can definitely vary from dog to dog based on multiple criteria. For loops follow this syntax. Zig has a built-in function for just this purpose: @fieldParentPtr. Hence, passing it as a parameter to a function will fail to compile. c --library c --verbose-cc real 0m0. You can use both directly on an array value and an array pointer interchangeably. Dec 14, 2023 · The unit test framework using in this post is MS CppUnitTestFramework 2. Use slices in all other cases. Types. Noncopyable. Chapter 4 - Learn about how the Zig programming language makes use of C code. We tell @fieldParentPtr the struct type (PickRandom), the name of the member ("interface"), and the pointer we have (iface). reserve(10); for( int i = 0; i < 10; ++i ) stuff. Let's take a look at the new next method that uses it. This is not theoretical, people routinely get bitten by this. Like while, for loops can use break and continue. share of ownership. // Create the object and pass it to a smart pointer std::unique_ptr<LargeObject> pLarge(new LargeObject()); Apr 10, 2023 · Zig Pointer Cheat Sheet for personal reference. And then there are many-item pointers. *. It doesn’t trigger too often since I’m using smart pointers most of the time (also I’m a supergenius), but when it does, it saves me hours of debugging. Using them can corrupt memory. Instead, when a smart pointer goes out of scope, it automatically handles the deallocation of the memory it manages, similar to how local stack variables are treated. Although lasers are silent, they can dupe a speaker into picking up sound container of smart pointers objects pointing to another. zig Aug 2, 2021 · This is useful when you want to free the memory owned by the smart pointer before the smart pointer goes out of scope, as shown in the following example. 027s user 0m0. c int* will be zig [*c]c_int, or c uint8_t* will be zig [*c]u8 Aug 8, 2023 · I suggest you avoid casting the function pointer and instead cast just the argument. In reverse direction, zig also provides common c types like c_int etc, as their size (or alignment) is platform dependent. Instead, it uses a modern, as of 2022, concept known as optional types, or smart pointers. > Zig aims to provide performance similar or better than C, so GC and ARC are not suitable solutions. Catch2: A modern, C++-native, test framework for unit-tests, TDD and BDD - using C++14, C++17 and later (C++11 support is in v2. 6 comments. meta. All smart pointers, including scoped pointers, have two states: empty and full. It kind of makes sense - Rust is a language that is made around the idea of writing safe code 99% of the time and only using unsafe code when absolutely needed, while Zig is a language made around the idea of writing unsafe code in an ergonomic and easily testable way. A pointer is a variable that points to something in memory. Jan 4, 2012 · To avoid memory leaks you may use smart pointers whenever you can. 018s sys 0m0. Unlike *T, it cannot point to a type that does not have a known size. This means that the value passed to that function parameter must be known at compile time. object with a smart pointer. There is no single smart pointer type, but all of them try to abstract a raw pointer in a practical way. A pointer is a value that holds the address of another value. Creating Unique Pointers with make_unique. Robust - behavior is correct even for edge cases such as out of memory. Zig automatically parses the . x branch, and C++03 on the Catch1. The C++ Standard Library provides powerful tools called smart pointers that… Dec 23, 2017 · Passing smart pointers is a critical topic that is seldom addressed. Must be comptime -known. zig 1/1 test "pointer to non-bit-aligned field" OK All 1 tests passed. However if you have an overaligned pointer to a packed struct, Zig should correctly understand the alignment of fields. Alignment § Each type has an alignment - a number of bytes such that, when a value of the type is loaded from or stored to memory, the memory address must be evenly divisible by this number. zig 1/2 test_pointer_arithmetic. for more information about Qt smart pointers visit this -> wiki. Let's make a function that returns a type. Nov 4, 2019 · November 4, 2019. In the future it will contain things such as: - Calling C code from Zig and vice versa - Using zig build with a mixture of C and Zig code. A smart pointer owning no object is said to be empty, and can be converted to false. Ultimately, we have only four rules that make our life as . The smart pointer will delete the pointed-to object at the right time, including invoking the object’s destructor. https://cppcon. And these are used in some of the projects. boost::scoped_ptr / std::auto_ptr) The main difference is that reference counted smart pointers can be copied (and used in Start your software dev career - https://calcur. This ends with the C++ core guidelines because they have six rules for passing std::shared_ptr and std::unique_ptr. Taken from ziglings #54 u8 | one u8 Tagged with zig, cheatsheet, pointer. Start using raw pointers to implement the data structures and write test code that uses them. A pointer is a general concept for a variable that contains an address in memory. Oct 30, 2022 · Starting with 0. /SLList 3 Last line of the program. Zig may be more flexible to use, like C, without having to consider as many safety factors. There are basically 2 different types of smart pointers in C++. This is one reason we prefer slices to pointers. Probably for similar reasons I don't like how RAII works in C++. Using this function is the preferred way of creating unique pointers: #include <memory> int main() { auto Pointer { std::make_unique<int>(42) }; } The < and > within this code indicates that make_unique is a template function. And by the way, may I ask a question here @ZigRazor ? I'm confused about dynamic allocated memory in part of benchmark-related code. zig 1/1 test "pointer to non-bit-aligned field"OK All 1 tests passed. They learn quickly and are able to perform many tasks and analyze situations. I think I get the basic principle: if I declare a var inside a function, the value is allocated on the stack, attached to the frame of the current function. Clear - precisely communicate your intent to the compiler and other programmers. These can help you manage memory. MyObject *object = new MyObject(this); object->setSomething(); // And you don't ever need to access it later. When the function exists, the stack is A smart pointer is a pointer that provides additional features beyond a traditional pointer, such as keeping track of the memory that the smart pointer points to. Researchers have found a way to hijack smart speakers by shining a laser at their built-in microphones. As for less memory, I think this is simply a clear win for Zig. #include <memory> // Declaring and defining a unique May 22, 2013 · All dynamic allocations should be hidden by the Standard Library, either with containers like std::vector or with smart pointers. Similarly, namespaced functions also do the right thing when invoked. { . A ring of objects can point to each other with weak_ptrs, which point to the managed object but do not keep it in existence. Generally, I would say that C++ and Zig are in the same performance ballbark, but my (obviously biased) position is that the Zig language guides you away from bad habits where as C++ encourages them (such as smart pointers and reference counting). Jan 25, 2024 · They are simple to deal with. But only RAII will allow for smart pointers and automatic (not manual) reference counting. Slices have bounds checking and are therefore protected against this kind of undefined behavior. This is the most correct answer if the goal is to study C++. Then, use smart pointers and observe the difference. 2 is unique to zig. By overloading *, ->, [], etc. The second means that only one smart Nov 9, 2020 · Pointers and pointer arithmetic. You can’t perform that action at this time. I don't know for C, but I work on a 5MLOC C++ very active project, and in my experience memory errors are not so frequent, especially after C++/11. You can defer cleanup to the end of a block; and this is half of the problem. C++11 introduced smart pointers like std::unique_ptr and std::shared_ptr, which automatically manage memory, reducing the risk of leaks. This automatic memory management emulates the convenience of stack variables and ensures safer code by reducing For loops. Aug 31 '22. zig 1/2 test "pointer casting" OK 2/2 test "pointer child type" OK All 2 tests passed. Zig (programming language) Zig is an imperative, general-purpose, statically typed, compiled system programming language designed by Andrew Kelley. There are three types of smart pointers in C++, shared pointers, unique pointers and weak pointers. md at main · thi-ng/blog. Conceptually, smart pointers are seen as owning the object pointed to, and thus responsible for deletion of the object when it is no longer needed. This feature is the key to make elegant boundary crossing possible as suggested by this article. I just chose to use a struct for fun, and it also shows how to annotate the type. eql is used here to check for equality between two vectors (also useful for other types like structs). zig Apr 21, 2013 · A vector of NULL pointers: std::vector<int*> nulled(10); A vector of pointers to newly allocated objects (not really initialization though): std::vector<int*> stuff; stuff. For example: const std = @import("std"); fn foo(str: []const u8) void {. Slices are similar to arrays since they also store a pointer and a length, but the length is only known at runtime, while the length of arrays is always known at compile-time. In Zig, we generally prefer Slices rather than Sentinel-Terminated Pointers. Optional pointer and optional slice types do not take up any extra memory compared to non-optional ones. Most languages today forbid this and often have dumbed down or heavily restricted versions such as Java references. Normal pointers in Zig cannot have 0 or null as a value. It ensures that at any given time, only one std::unique_ptr object owns the resource. This chapter is incomplete. tech/dev-fundamentals Be notified of new C/C++ course: https://calcur. //character literals are equivalent to integer literals. The functions can access this data using @fieldParentPtr. [4] May 2, 2022 · So it's probably going to shade over, C++ code that's mostly 15-20 years old may be happier to work with from Zig, while C++ code that's all written after say C++ 14 might be much easier to work with from Rust via one of the C++ FFI libraries like cxx which understands the standard library smart pointers. Smart Pointers are like the upgraded version of these foundational elements. The smart pointer library provides six smart pointer class templates: Simple sole ownership of single objects. I tried to use @as, but apparently that's wrong. So a *u8 points to a u8. You don't need/want to store the pointer. print("{s}\n", . From Zig SHOWTIME #13Subscribe to the Zig SHOWTIME Newsletter!https://zig. Slices are used heavily throughout Zig for when you need to operate on arbitrary amounts of data. d file uses a robust caching system to avoid duplicating work. Consider the following example: Sep 24, 2023 · I'm trying to rewrite a program in Zig, but I don't know how to use pointer cast. debug. Manual memory allocation and deallocation. : Slices. It creates a dichotomy between normal objects and smart objects, just like this proposal makes certain functions require special treatment. cpp -o SLList 2 ~ $ . g. In Zig the dot works for both struct values and struct pointers transparently. The first is the exact same situation in which you should not use a C++ class in fact. The most common kind of pointer in Rust is a reference, which you learned about in Chapter 4. boost::shared_ptr / std::tr1:shared_ptr) non reference counted (e. IE: DLL boundary if you do not offer the source code to the client. Unique Pointers. •. C++11 includes a solution: "weak" smart pointers: these only "observe" an object but do not influence its lifetime. Vectors can only have child types of booleans, integers, floats and pointers. GLFWwindow, _: c_int, _: c_int) callconv(. As a function pointer. From this perspective, Zig’s safety measures for pointers are similar to Rust’s references. qt. If needed, you can generate a wrapper function with the correct type that does the cast. Zig by Example. test. wt ll lm yi uv kb tm ee gi hm